How could this have happened to my high school photo?

Did your daughter try to help you out by cleaning some trash from your car, accidentally dumped the picture, then someone put more trash on top?

Good theory. No; we didn’t clean out the car. Knowing her personality as I do, I believe she could very well have picked up the photo and put it in the trash when I wasn’t looking. But that doesn’t explain why I looked in the trash the next day . It never dawned on me at that time she could have put it in there. I was stunned when I found it. It was like I was seeing things that weren’t there.
Furthermore, when I told her I found it and where she was silent.

Well, you seem to know that your daughter isn’t the nicest and how your picture ended up in the trash.

yes, but why would I look in a trash barrel? I didn’t look underneath the car which would seem to have been a better choice. And I did not think she’d do such a thing. What was there for her to accomplish? I wasn’t throwing anything out. I just took the lid off and searched down in the layers of paper. Oh, well. Stranger things have happened.

Instinct. Perhaps she doesn’t like that photo of you?

I don’t know. I just remain amazed that I found it. It’s so small and to think I could even see it amongst all that trash. I wasn’t even looking in there to throw something away. I just lifted up the lid for seemingly no reason. Weird.

In fairness to your daughter, perhaps it had blown off the dash and she collected some rubbish up and accidently picked it up and put the rubbish (and it) in the trash. Good that you found it anyway. You are obviously meant to keep it.